Dicamba is a selective herbicide currently used for treating e.g. corn, wheat or grassland. It kills broadleaf weeds before and after they sprout. The trivial name dicamba refers to the compound 3,6-dichloro-2-methoxybenzoic acid. The estimated global demand for dicamba in 2012 was about 12.000 metric tons per year. However, it is expected that the global demand for dicamba will increase significantly.
Dicamba is typically produced on an industrial scale via 2,5-dichlorophenol and using carboxylation under Kolbe-Schmitt conditions, methylation and subsequently saponification/acidification. 2,5-Dichorophenol in turn can be obtained from 1,4-dichlorobenzene or 1,2,4-trichlorobenzene. A synthetic route via 1,4-dichlorobenzene involving nitration and subsequent diazotation may, however, be undesired for use on an industrial scale. A synthetic route via 1,2,4-trichlorobenzene may suffer from limited availability of this starting material and from the formation of several byproducts which are formed in the synthesis of 2,5-dichlorophenol.
There is a need in the art for an efficient process for obtaining 2,5-dihalogen substituted phenols, such as 2,5-dichlorophenol.